Metallized rocket propellants containing azides



United States Patent 3,288,659 METALLIZED ROCKET PROPELLANTS CONTAININGAZIDES Douglas A. Rausch, Midland, Mich., assignor to The Dow ChemicalCompany, Midland, Mich., a corporation of Delaware No Drawing. FiledJan. 24, 1962, Ser. No. 169,180 3 Claims. (Cl. 14936) This inventionrelates to rocket propellants and more particularly is concerned with animproved rocket propellant based on a metallized-inorganic oxidizersystem.

The use of metallic fuels in combination with inorganic oxidizers assolid propellants is Well known and widely used. For example, finelydivided metals such as aluminum, magnesium, zirconium, beryllium,lithium and the like either alone, as mixtures or as alloys when admixedwith ammonium nitrate, ammonium perchlorate, lithium perchlorate orother inorganic oxidizers provide solid propellants which upon burninggive large amounts of heat. However, these systems have relatively smallamounts of gaseous products and therefore the specific impulse of thesepropellant systems is relatively low.

The addition of enhancing materials to such systems to provide lowmolecular weight 'gaseous products has been disclosed generically in acopending application Serial No. 846,510, now Patent No. 3,151,445,filed October 14, 1959. Now, it has been found that the particular solidcompounds, hydrazonium azide (N H -N H) and/ or hydrazonium azidehydrazide (N H -N H-N H are highly satisfactory driving fluids for usein conventional metallized propellant systems. These specific solidcompounds serve to markedly increase the specific impulses of suchsystem since they provide large amounts of low molecular weight gasesupon combustion of the propellant.

The amount of the hydrazine based azide compound to be incorporated intothe metallized propellant system is that quantity which utilizes and isexpanded by the waste heat of combustion that ordinarily goes to produceundesirable phase changes and/ or dissociation of the propellantcombustionproducts while maintaining the combustion flame temperature ata minimum of about 3000 K. However, depending upon the characteristicsdesired in a propellant system either larger or smaller amounts of thehydrazonium azide or hydrazonium azide hydrazide can be employed in thesystem. For example, with an aluminum-ammonium nitrate propellant forthe optimum specific impulse the amount of hydrazine azide compound tobe employed is from about 1 to about 1.25 moles per mole of aluminumoxide produced. With an aluminumammonium perchlorate propellant, fromabout 1 to about 2 moles of the azide compound preferably is to beemployed per mole of aluminum oxide produced.

The azide gas formers, or driving fluids as they are called, can be usedboth with simple mixtures of the inorganic oxidizer and metal or withpropellant formulations having binders and other components therein.Ordinarily, the metal-inorganic oxidizer solid propellants arestoichiometrically balanced for metal oxide formation although incertain instances these may be oxygen rich. The hydrazine azides can beadded to the propellant during formation of the propellant grain as apart of the general blending procedure or can be added at the timesduring the propellant manufacture as is apparent to one skilled in theart.

The utility of the instance additives is shown further by the followingexamples. An aluminum-ammonium perchlorate solid propellant,stoichiometrically balanced 3,288,659 Patented Nov. 29, 1966 forconversion of all the aluminum into aluminum oxide according to thefollowing tquation (I) has an undesirably high calcuated combustiontemperature of about 5500 K and a specific impulse of about 261 seconds.

Adding hydrazonium azide hydrazide to this composition in an amount toprovide a combustion temperature of about 3800 K. gives a calculatedspecific impulse of 285 seconds.

If hydrazonium azide is incorporated into a similar aluminum-ammoniumperchlorate propellant to give a combustion temperature of about 3800 K.the calculated specific impulse is 283 seconds.

In a manner similar to that described for the foregoing exampleshydrazonium azide can be incorporated into an aluminum-lithiumperchlorate based propellant system. Hydrazonium azide hydrazide can beadded to an aluminum-ammonium nitrate propellant having a polyurethanebinder. Likewise the hydrazine based azides can be added to (1)magnesiumdithium perchlorate solid propellant, (2) lithium-ammoniumperchlorate and (3) aluminum-ammonium nitrate-ammonium perchloratesystems.

Various modifications can be made in the present invention withoutdeparting from the spirit or scope thereof for it is understood that Ilimit myself only as defined in the appended claims.

I claim:

1. A solid rocket propellant composition consisting essentially of afinely divided light metal and an inorganic oxidizer selected from thegroup consisting of ammonium perchlorate, ammonium nitrate, lithiumperchlorate and mixtures thereof, said light metal and inorganicoxidizer being present in stoichiometric amounts based on the conversionof said metal to the corresponding metal oxide, and in admixturetherewith a gas producing member selected from the group consisting ofhydrazonium azide, hydrazonium azide hydrazide and mixtures thereof,said gas producing member being present in amount which utilizes and isexpanded by the waste heat of combustion of said propellant whilemaintaining the combustion flame temperature of said propellant at aminimum of about 3000 K.

2. A solid rocket propellant composition consisting essentially of astoichiometric mixture of finely divided aluminum and ammoniumperchlorate and having hydrazonium azide in combination therewith, theamount of said hydrazonium azide in said composition ranging from about1 to about 2 moles per mole of aluminum oxide produced by combustion ofsaid propellant.

3. A solid rocket propellant composition consisting essentially of astoichiometric mixture of finely divided aluminum and ammoniumperchlorate and having hydrazonium azide hydrozide in combinationtherewith, the amount of said hydrazonium azide hydrazide in saidcomposition ranging from about 1 to about 2 moles per mole of aluminumoxide produced by combustion of said propellant.

References Cited by the Examiner UNITED STATES PATENTS 4/1961 Boyer149--35 8/1961 McMillan et al. 149-22 X BENJAMIN R. PADGETT, PrimaryExaminer.

1. A SOLID ROCKET PROPELLANT COMPOSITION CONSISTING ESSENTIALLY OF AFINELY DIVIDED LIGHT METAL AND AN INORGANIC OXIDIZER SELECTED FROM THEGROUP CONSISTING OF AMMONIUM PERCHLORATE, AMMONIUM NITRATE, LITHIUMPERCHLORATE AND MIXTURES THEREOF, SAID LIGHT METAL AND INORGANICOXIDIZER BEING PRESENT IN STOICHIOMETRIC AMOUNTS BASED ON THE CONVERSIONOF SAID METAL TO THE CORRESPONDING METAL OXIDE, AND IN ADMIXTURETHEREWITH A GAS PRODUCING MEMBER SELECTED FROM THE GROUP CONSISTING OFHYDRAZONIUM AZIDE, HYDRAZONIUM AZIDE HYDRAZIDE AND MIXTURES THEREOF,SAID GAS PRODUCING MEMBER BEING PRESENT IN AMOUNT WHICH UTILIZES AND ISEXPANDED BY THE WASTE HEAT OF COMBUSTION OF SAID PROPELLANT WHILEMAINTAINING THE COMBUSTION FLAME TEMPERATURE OF SAID PROPELLANT AT AMINIMUM OF ABOUT 3000*K.